Linear voltage generator



March 20, 1934. MCL co 1,951,525

LINEAR VOLTAGE GENERATOR Filed April 14. 1931 2 Sheets-Sheet l Elc2 l INVENTOR 1 Alexanggr M Lean Niuulsu \M/ZMW ATTORNEY March 20, 1934. A. M L. NICOLSON LINEAR VOLTAGE GENERATOR Filed April 14. 1931 2 Sheets-Sheet 2 TIME 5 INVENTOR Alexander MEL-EH11 Niculsun M/f MW ATTORNEY I Patented Mar. 20, 1934 UNETED STATES rarest orrics LINEAR VOLTAGE GENERATOR Application April 14,

12 Claims.

This invention relates to the generation of electrical voltages and currents, and particularly to the generation of such voltages having a linear variation with respect to time.

An object of the invention is to generate varying electrical voltages and currents.

Another object of the invention is to generate electrical voltages and currents having linear or straight line characteristics.

A further object of the invention is to generate electrical voltages and currents having a periodic or cyclic variation with a linear characteristic between maximum and minimum values.

I have disclosed in my copending application Ser. No. 505,539, filed December 30, 1930, apparatus for and means of generating cyclic varying frequencies having a uniform linear variation. This invention is related to such generators but provides a simple and efficient manner of obtain- 20 ing directly from an amplifier a voltage variation which increases or decreases uniformly over a definite time interval. This system also provides for cyclic variations of different frequencies, the variation in voltage between maximum and minimum values being linear.

To control the oscillator disclosed in the abovementioned application, a moving electrical discharge or arc between electrode rails in a magnetic field was employed. The same type of con- 30 trol is employed in this invention, the arc rails being given a definite curvature with respect to a central point in the same plane as the rails. This curvature may be extended into a spiral depending upon the particular voltage output characteristic desired. The central point in the plane of the curve or spiral is provided with a photoelectric cell or similar light detector having a.

where I is the intensity, a a constant depending on the light source and the transmission medium,

and r the distance between the light source and 1931, Serial No. 529,902

the observer, the principles of the present invention are based.

The invention will be more fully understood by reference to the following description in conjunction with the accompanying drawings, in which:

Fig. 1 is a plan view of the generating system;

Fig. 2 is an elevational View of the same apparatus as shown in Fig. 1;

Fig. 3 is a development of the curvature of the arc rails employed in the system;

Fig. 4 is a graph of the output voltages tained with the system; and

Figs. 5, 6 and 7 are views of modifications of electrode rail configurations.

Referring specifically to Figs. 1 and 2, an annular photoelectric cell 5 which may be of any suitable type responsive to either visible or invisible light or both, is shown centrally disposed in the arc system. This cell may be a Westinghouse type VB, the cathode and anode being constructed in .annular form such that the cathode has a concave section outward similar to an inner half section of a hollow toroid while the anode is a single fine wire positioned anteriorly thereof. The photoelectric cell output is impressed upon an amplifier 6 for amplification, the amplifier having output terminals '7. The electrodes employed in the system are shown in the spiral-like path 10 with a starting gap at the point 11 and with blow-out terminals 12. It is to be understood that the starting gap and blow-out terminals may be reversed, the travel of the are being accomplished in the reverse direction by reversal of either the field or arc potentials. The are rails 10 are connected to a source of polarizing potential 15 under control of a rheostat 16 for increasing or decreasing the arc current, and con sequently the speed of the are. A field producing coil 18 wound on a core 19 is supplied from a source of energy 20 under control of the rheostat 21 for increasing or decreasing the strength of the field.

This field structure produces between the arc electrodes a flux which is perpendicular to the arc and applies thereto a force which is substantially parallel with the arc rails, the .arc being driven therealong in the well known manner. It is to be understood that a similar coil producing a similar field may be positioned so as to oppose the coil 18 to create a stronger field for the are. When using two field coils it is necessary to have like poles adjacent one another to produce the fringing flux perpendicular to the arc position. By controlling the field strength by rheostat 21 and the arc current by rheostat 16,

it is possible to alter the speed of the are along the rails and its intensity to produce any cyclic variations of the output voltage desired.

In Fig. 3 is shown a practical method of obtaining the proper spiral for constructing the arc rails. The construction of the curvature 'of the electrode rails must be such that as the arc is propagated along the rails at a constant velocity, the intensity of illumination decreases at a uniform rate, producing in the photocell a linear decrement in output current. Therefore, a relationship must be obtained between a unit length of arc path and the distance between the light source and the cell. Since the intensity of light varies in accordance with the inverse square law, we have the above-mentioned-equation Assuming S as the length of the arc path we desire the following relationship between intensity and S.

where b is a constant depending on the type of light source and the transmission medium. Solving for S from Equations (1) and (2) we obtain S=Kt 4 where K represents the combined constants a and b.

The curve of Fig. 3 has been developed from the Equation (5), assuming K to be unity, with the following tabulated values obtained from the equation.

The point X is, therefore, obtained by locating on a circle having a radius of 2 units a distance of 4 units along the previously developed spiral. So on for points Y and Z which have a radius of 3 and 4 with an arc path of 9 and 16, respectively. When the angle of rotation is small the chord is practically equal to the subtended curve, permitting an extremely accurate construction by this approximation.

The theoretical curve may be obtained in the polar form from which the radius r for any angle may be readily calculated. We start with the equation for the length of arc in terms of the angle and the radius vector 1' Then with the aid of Equation (4) after performing the required integrations, we obtain the where 0 is expressed in terms of 1".

Referring to Fig. 4, the solid curve a illustrates the voltage output at the terminals '7 of Figs. 1 and 2. The highest maximum voltage out" put is produced at the time the arc is created at the point 11 and decreases linearly to point 12 as the arc progresses along the electrodes 10. The starting gap is always some distance from the photoelectric cell. Immediately upon the ex tinguishing of the are at point 12 it is created at the point 11, in reasing substantially instantaneously to the maximum voltage for the next cycle. The dotted curve 5 in this figure illustrates an increasing linear potential which may be produced with the same are system except that the arc is created at the point 12 and blown out at the point 11 to produce a reversal of the voltage characteristic. It is only necessary to change the direction of either t -e field or the potential on the electrode rails to accomplish this reversal. The time between maximum and minimum points is determined by the field strength or current in the arc, the dotted curve 1) showing a system in which thecurrent has beenlowered to produce a lower maximum than formerly but the field has been strengthened to produce shorter time intervals between cycles. t is possible, therefore, to obtain substantially any cyclic frequency at different amplitudes within the limits of the system. 1

The broken curve c in Fig. 4 shows the relationship between voltage and-time obtainable with a continuous arc rail system such as shown in Fig. 5. Through an angle of 186, the arc will increase to its maximum distance from the cell 5 and decrease to its minimum distance through the remainder of its cycle. The curvature is the same as that developed in the system of Fig. 3 with a reflection of the curve constituting the return path to continue the linear relationship. The starting gap may be at either point 25 or 26. Of course, the arc may bemade to return along the same outward path by having a double rail system, the inner rail of which is common to both paths, as shown in Fig. 6 in elevation.

If combination linear and higher plane characteristics are desiredfor variations in voltage, such as illustrated in curve 01, Fig. 4, are rails having configurations to conform thereto may be employed. Fig. 7 illustrates an arc path to obtain the voltage-time characteristic shown in curve (1. By'a double return as shown in Fig. 6, a symmetrical characteristic is obtainable.

Systems having such voltage-time characteristics may have many useful applications and are especi ally desirable in such multi-channel transmission systems as disclosed in my copending application Ser. No. 517,383, filed February 21, 1931. Certain voltage limits may control transmission of signals by causing the operation or blocking of certain vacuum tubes in a multi-channel signalling system. There are many other applications which will be obvious to those skilled in the art, and it is to be understood thatthe invention is to be limited only by the scope of the appended claims.

What is claimed is:

1. An electrical current generator comprising means for creating a magnetic field, a set of electrode rails disposed in said field, means for creating an electrical discharge between said electrodes, and means for detecting the light from sa d discharge, said electrode rails having a configuration that varies the distance between said discharge and said detecting means as a predetermined function of the illumination on said detecting means.

2. In an electrical current generating system, means for creating a magnetic field, a photoelectric cell for detecting light, a pair of electrode rails located in said field, and means for creating an are on said rails, said pair of electrode rails being designed to define the path of said arc in a manner to vary the intensity of the light of said are on said cell in a linear relationship.

3. In an electrical current generating system, a pair of spiral shaped electrode rails, means for creating an electrical d scharge between said rails, means for creating a magnetic field in which said rails are positioned, and a photoelectric cell positioned at the center of said system to detect the light from said electrical discharge.

4. In combination, means for creating a uniform magnetic field, a set of electrode rails positioned within said field, means for polarizing said electrode rails to form an electrical dscharge therebetween, said discharge being propagated along said rails by said magnetic field, and a photoelectric cell positioned in the plane of said rails for detecting light from said discharge, said electrode rails having a configuration that varies the position of the discharge from said cell in accordance with the inverse square law between light intensity and distance.

5. In combination, means for creating a magnetic field, a photoelectric cell, and a pair of electrode rails located in said magnetic field, the distance from point to point between said electrode rails and said photoelectric cell varying as the square of the radius from said cell.

6. In combination, means for creating an electromagnetic field, a photoelectric cell, a pair of electrodes in said magnetic field, and means for polarizing said electrodes to produce an electrical discharge therebetween, said means being formed to create said discharge at a point nearest the photoelectric cell and to extinguish said discharge at a point farthest from said photoelectric cell.

7. In combination, means for creating a magnetic field, a photoelectric 'cell, a set of electrodes in said magnetic field, said photoelectric cell being centrally disposed in the plane of said electrodes, and means for polarizing said electrodes to produce an electrical discharge therebetween, said electrodes having a configuration which varies the illumination from said discharge on said cell non-uniformly.

8. In combination, means for creating a magnetic field, a photoelectric cell, a pair of electrodes in said magnetic field encircling said cell, and means for polarizing said electrodes to produce an electrical discharge therebetween, said electrode rails determining a path for said are with respect to said cell which uniformly increases the current generated by said cell over portions thereof and produces a constant value of current in said cell over other portions.

9. In an electrical generating system, means for transforming light intensities into electrical currents, means for creating a magnetic field, a pair of electrodes positioned in said field, and means for producing an electrical discharge between said electrodes, said electrodes determining a path for said electrical discharge which varies the current generated in said transforming means in a predetermined wave pattern.

10. The method of generating from a light sensitive device cyclic voltage variations having definite characteristics between maximum and minimum values from an electrical light source of constant intensity comprising propagating said electrical light source of constant intensity relatively to said device to produce a predetermined light variation on said device and transforming the light from said source into electrical variations.

11. The method of generating from a light sensitive device cyclic voltage variations of a predetermined character from a light source of constant intensity comprising propagating said light source of constant intensity to produce on said device non-uniform light variations and transforming by said device said light variations into electrical currents.

12. In combination a photoelectric cell for detecting light from any point in a certain plane, means for producing a moving electrical light source, and means for predetermining the path for said source of light to vary its distance from said cell, said cell being actuated at different light intensities in accordance with a predetermined path of said source.

ALEXANDER MCLEAN NICOLSON. 

